The present invention relates to devices and methods for treating cardiomyopathy, a chronic disorder of the heart muscle, and more particularly to an implantable ventricular restraint device which is adapted to confine and control ventricular diastolic expansion.
Cardiac dilation occurs with various diseases of the heart, including heart failure. In some instances, such as ischemic heart disease, the dilation may be localized to only a portion of the heart. On the other hand, cardiomyopathy usually results in global impairment. In the case of hypertrophic cardiomyopathy, there is typically increased resistance to filling of the left ventricle with accompanying dilation of the left atria. In dilated cardiomyopathy, the dilation is typically of the left ventricle with resultant failure of the heart as a pump. As the ventricles become enlarged, the situation is worsened by the resultant leakage which develops around the valvular structures. A sharply reduced ejection fraction is the hallmark of this condition.
Dynamic cardiomyoplasty is one treatment currently being used to treat cardiomyopathy. One current approach being used to treat this disorder is a procedure that involves wrapping and attaching a portion of a patient""s own latisimus dorsi muscle around the heart, as described, for example, in the article Reverse Remodeling from Cardiomyoplasty in Human Heart Failure, Circulation, May 1, 1995, Vol. 91, No. 9 (Kass et al.). A pacemaker-like electrical stimulator is then attached to both the heart and the wrapped muscle. After a healing period, the wrapped muscle is electrically stimulated in synchrony with the heart which causes the muscle to contract at the appropriate time. This action actively squeezes the ventricles of the heart, to augment their function. A reversal of the heart""s chronic dilated condition has been found to result in many cases, and current medical opinion is that patients with chronic heart failure may be cured of symptoms by providing assistance to ventricular function using this or similar methods. Some have also considered the benefits of merely wrapping or constraining the heart with skeletal muscle without providing active systolic assist. In any event, it will be appreciated that, although this method of treatment has proven effective, it is an open surgical procedure, which involves both removal of the patient""s latisimus dorsi muscle and reattachment of the same to the heart. The frequency of the electrical stimulation, if employed, is the only adjustment that a medical professional can make to optimize the treatment for individual patients using this technique.
Another approach which has been considered to address this disorder is disclosed in U.S. Pat. No. 5,702,343 to Alferness. This patent discloses a device comprising a jacket of biocompatible material, which is applied to and adjusted to fit the epicardial surface of the heart. The device, once placed, controls cardiac expansion to a predetermined size. In one embodiment, an inflatable member is provided which is mounted between the jacket and the epicardium for selectively adjusting the size of the jacket as the heart remodels and reduces in size responsive to treatment, but there is no disclosed or suggested provision for regulating the size of the device without surgical intervention. In many cases, by the time it becomes evident that the patient is in need of treatment for cardiomyopathy, the dilation has already occurred and the patient is in chronic disorder. If the constraining device cannot be effectively and easily resized as the heart begins to remodel, it may not continue to be effective, and the possibility for a maximum remodeling of the heart may be reduced. Another drawback to the disclosed approach of Alferness is that the disclosed device applies a uniform force to both right and left ventricles. Typically, the left ventricle is the one that causes the disorder as it operates at much higher pressures. This design does not provide the medical professional with any means to accurately optimize or monitor the device""s therapeutic effect. The optimal operating parameters for the device may vary dramatically from patient to patient, and these parameters can again change over time as the patient""s heart becomes accustomed to the device or goes through a remodeling phase. There is typically a very small imbalance in operating forces that causes the problem and therefore a very small force is sometimes all that is required to correct the condition. Consequently, in the event that the patient were to have an adverse reaction to the device""s preset configuration, an urgent surgical intervention would need to be performed to remedy the problem.
What is needed, therefore, is an improved ventricular reinforcement device which may be conveniently re-sized without surgical intervention as the heart remodels to its normal size, and which is capable of independently applying selectively differing forces against the right and left ventricles of the diseased heart.
The present invention addresses the problems outlined above by providing a unique device for treating heart disorders, and particularly cardiomyopathy, comprised of a compliant containment structure shaped in a configuration such that it surrounds and encases the heart. Within this containment structure are housed two or more inflation pockets that are fabricated from a non-elastic compliant material. These pockets are disposed on the interior surface of the containment structure and are configured to oppose and support the external wall of at least one of the ventricles of the heart. In the preferred embodiment, there are a plurality of relatively small, spaced inflation pockets disposed to act against each ventricle which is to be contained.
On the external surface of the containment structure, or spaced therefrom, there is disposed a recoil balloon, which is configured from an elastomeric material. The containment structure physically separates the inflation pockets from their associated recoil balloon(s). However, a fluid flow path is provided between the pockets and their associated balloon(s). Each recoil balloon has an inflation delivery tube which is in turn fluidly connected to a fluid access port which delivers fluid to the device as needed.
The invention, together with additional features and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying illustrative drawing.